This invention relates generally to platform scales, and, more particularly, to heated vehicle platform scales.
Modern platform scales for trucks or other vehicles frequently employ strain gauge technology, whereby weight is measured by means of strain gauge transducers, or load cells. The platform is supported by load cells spaced from one another, each of which is typically mounted within an enclosure and supported therein so that the load cell is capable of deflection as weight is applied to the platform. Strain gauges mounted on the load cell sense load cell deflection and provide electrical signals related thereto. The electrical signals are combined, amplified if necessary, and supplied to an indicator which provides a display of the weight borne by the platform.
Such scales are preferred over other types of scales because the read-out is nearly instantaneous and requires no manual operations. These scales are typically installed at truck stops or service stations where it is desired that a high throughput rate of vehicle weighing by possible with a minimum amount of service help.
A vehicle platform scale is typically installed with the load cell enclosures recessed into an approach surface such that the platform is flush with the surface. A scale pit is sometimes employed under the scale. A pair of scales is generally used, the scales being aligned parallel to one another and spaced apart by such a distance as to accommodate the right and left sets of wheels of a standard truck or other vehicle. In practice, the vehicle is rolled onto the scales and the weight borne by each axle is measured as its wheels pass over the scales.
In cold climates, it has been found that ice and snow sometimes accumulate inside the load cell enclosures and impair the operation of the scale. This accumulation may occur by the action of wind blowing snow into the enclosures or by the action of water running into the enclosures and subsequently freezing. In either event, the ice or snow builds up under the load cells, thereby limiting or otherwise affecting their downward deflection and causing the scale to function improperly.
The build-up of ice or snow occurs where it is hidden from view. Thus, the build-up often goes unnoticed for relatively long periods of time, during which weight measurements may be rendered inaccurate by the build-up, and is often detected only after the weight readings become so grossly erroneous as to alert the scale operator to the malfunction.
In practice, it has been found difficult to avoid this problem. The scales must necessarily be independently supported and detached from the roadway, making it almost impossible to prevent water from seeping into the scale pit or into the load cell enclosures and freezing therein.
Prevention of ice or snow accumulation requires frequent inspection and maintenance, resulting in undesirable down-time and a lower throughput rate. Furthermore, once ice has accumulated it is difficult to remove and results in significantly greater delays in operation.
Further, it has also been found that wide temperature fluctuations are in and of themselves causes of inaccuracies in the function of the platform scales. Wide temperature fluctuations cause expansion and contraction of the load cells and other parts of the platform scale, thereby requiring frequent calibration of the scales.
In view of the foregoing, it is, accordingly, an object and purpose of this invention to provide a device which prevents accumulation of ice and snow in a load cell enclosure of a vehicle platform scale.
It is also an object of this invention to provide a device which maintains the load cell of a platform scale at a relatively constant temperature.
It is a further object of this invention to provide a vehicle platform scale which requires a minimum amount of periodic maintenance and inspection.